Twenty-one states, the District of Columbia and several public interest groups filed the first major lawsuits Tuesday to block the repeal of the Federal Communications Commission’s net neutrality rules, marking the start of a high-stakes legal battle over the future of the Internet.

The FCC's rules had prohibited Internet providers from slowing down or blocking websites. New York Attorney General Eric Schneiderman, who is leading the states' suit, said that the FCC’s repeal of the net neutrality rules was “arbitrary” and “capricious” and violates federal law.

The suit comes just a day after Democrats in the Senate said they were inching closer to the votes needed for a legislative measure to help overturn the FCC's rule change. Their resolution aims to reverse the FCC's decision and block the agency from passing similar measures in the future. It has garnered the support of all 49 Democratic senators as well as one Republican, Sen. Susan Collins of Maine.

Tuesday’s lawsuits seized on that momentum and represent another avenue for supporters of the net neutrality rules to undo the repeal.

The net neutrality rules were dismantled in a December vote led by Republican FCC Chairman Ajit Pai. Republicans had argued that the existing rules stymied industry investment, while Democrats maintained that they served as a vital consumer protection.

The FCC voted to repeal net neutrality, or the idea that Internet service providers can't block or favor websites. See what this means for you. (Jhaan Elker,Brian Fung/The Washington Post)

In Tuesday’s filing, the attorneys general requested that the U.S. Court of Appeals for the D.C. Circuit review the FCC’s new policy to determine whether it is illegal and unconstitutional.

Schneiderman argued in a statement that the FCC failed to justify its net neutrality reversal while dismissing evidence of harm to consumers and businesses. He also claimed that the FCC erroneously and unreasonably interpreted the Communications Act, the federal law at the heart of the net neutrality rules. In addition, Pai’s move to repeal the rules included an unlawful preemption of state and local regulations, Schneiderman said.

The FCC is expected to defend its decision by pointing to prior cases in which the agency had changed its mind on how to regulate businesses under its jurisdiction. Lawyers representing the broadband industry have said the FCC will have a strong case if it can demonstrate solid reasoning.

The FCC declined to comment.

The FCC gets a “significant amount of discretion” to switch directions on policy, said Matthew Brill, a partner at the firm Latham and Watkins who represents NCTA — The Internet and Television Association, a major cable industry trade group, in a recent interview.

“When the court ruled [last time],” said Brill, “it emphasized it wasn't assessing the wisdom of that policy — it was just upholding the agency's decision-making under the broad leeway it gets.”

Until the FCC's decision is published in the Federal Register — a process that could take days or weeks — appeals courts may reject any lawsuits submitted on net neutrality, on the grounds that it is too soon to file. But those filing the suits Tuesday said they issued their challenges to ensure their suits are included in the judicial lottery, the process that determines which court will hear the case.

In filing with the D.C. Circuit, the state attorneys general hope to “win” the lottery by having that court hear the case. It was the D.C. Circuit that upheld the FCC's net neutrality rules in 2016, handing the telecom industry a major defeat.

Outside defenders of the FCC, meanwhile, could launch their own court petition to have the rules reviewed. Doing so would allow industry groups to try to win the judicial lottery by having the case heard in a court that is considered friendlier to business interests.

All 22 attorneys general listed in the lawsuit are Democrats. In addition to the District of Columbia and New York, California, Virginia, Illinois, Pennsylvania, Connecticut, Delaware, Hawaii, Iowa, Kentucky, Maine, Maryland, Massachusetts, Minnesota, Mississippi, New Mexico, North Carolina, Oregon, Rhode Island, Vermont and Washington are all part of the suit.